Often, a marking engine may include a streak reduction or correction component (e.g., the Auto Density Control from Xerox or the like) to reduce streaks in prints. For systems that employ electronic registration, such as Side1/Side2 (S1/S2) magnification adjustment, the appearance of narrow streaks can actually be more pronounced when special steps are not taken to align compensation data. This can occur when one magnification factor is used when uniformity data is acquired and a different factor is used when the uniformity compensation is applied.
The streak reduction component may employ a form of spatially varying tone reproduction curve (TRC) that is used to compensate for streaking in a marking engine. Electronic registration can be used to scale an image to compensate for magnification effects and is used to scale a digital image to compensate for paper shrinkage in S1/S2 printing. One way that such electronic registration techniques are used is to apply an inverse paper shrinkage scaling to Side 1 of a print. That is, if the paper will shrink by a factor 0.998, a digital magnification of 1.002 will be applied to Side 1. After printing and fusing, Side 1 will be at nominal size. Assuming paper shrinkage is minimal for a second fusing, Side 2 can be printed at the nominal size to get S1 and S2 to be matched in size.
Using electronic registration with streak reduction presents a compensation alignment problem. For instance, streak reduction algorithms may be more practical at 600 spi, while the electronic registration algorithms achieve optimal image quality using a Vertical Cavity Surface Emitting Laser (VCSEL) Raster Output Scanner (ROS) with an output of 2400 spi.
If the non-uniformity calibration data is acquired with one electronic registration magnification factor (e.g., 1.0) but applied at another, the streak reduction compensation will be misaligned with marking process. More specifically, by way of example, the streak reduction component may be calibrated with an electronic registration magnification of 1.0, which is the current practice due to on-belt measurement of non-uniformity. When S1 is passed through the streak reduction component, the compensation is applied on a pixel-column-by-pixel-column basis assuming the compensation for a given column will be registered with the corresponding physical column in the marking process. If the image is then scaled up by 1.002 in the electronic registration software to compensate for subsequent paper shrinkage, the uniformity compensation applied to each pixel column will not be in register with the corresponding physical columns in the marking process.
Other printing and compensation scenarios can cause the same type of streak defect. For instance, even if spatial scale factors for Side 1 and Side 2 for a given paper are employed, changing the paper type without shrinkage recalibration could cause the streak defect unless new paper scaling parameters were provided for correction. There may be similar issues in print bar (LED or ink jet) uniformity compensation via TRCs in the presence of thermal expansion.
There is an unmet need in the art for convenient and easy-to-use systems and methods that facilitate aligning compensation data with non-uniformities in a scanned image to ensure that the compensation data is applied at the correct position on the scanned page.